Iran and five world powers agreed last week to extend by four months a deadline for reaching a final deal aimed at preventing Iran from acquiring a nuclear bomb. But a yawning gulf still has to be bridged.

Istanbul; and Tehran, Iran — Though diplomats from Iran and six world powers are talking up the “substantial progress” that led to an extension of nuclear talks until November, crucial differences still threaten a final deal to ensure Iran can never produce a bomb.

And it is not clear yet if the gap can be bridged over the scale of Iran’s future uranium enrichment given the insistence by both Washington and Tehran that the other side must make "hard choices" to clinch a deal.

Across Iran’s political spectrum there is wide support for the nuclear program – and for a comprehensive nuclear deal that removes sanctions from its struggling economy.

While conservatives frame Iran's nuclear program as a matter of "national dignity" that can't be traded, reformers also squirm under Western pressure to cap Iran's capacity. One Westernized industrial engineer – who sat recently with his lip-stick wearing girlfriend, watching a World Cup football match in a Tehran café – asked a journalist out of the blue: “Do you think Iran should give away its [nuclear] rights?”

When talks resume, US officials say they are seeking a “significant reduction” in Iran’s current operating capacity of some 10,000 centrifuges, which are used for the enrichment of uranium. In recent weeks, the US and five other world powers put on the table cutting Iran's capacity to as little as 500.

In turn, Iran’s supreme leader said in an unusually detailed assessment last week that Iran’s “absolute need” was instead nearly 20 times greater than current capacity, roughly the equivalent of 190,000 first-generation centrifuges, and that this was necessary to provide fuel for Iran's power reactor when a Russian supply contract expires in seven years. Iranian officials say any “dismantlement” of current enrichment capacity, or a permanent cap on future advances, would be seen as an unacceptable defeat at home.

Interim deal 'overperformed'

That chasm has changed little since Iran began negotiating three-and-a-half years ago, with the P5+1 group (the US, Russia, China, United Kingdom, France and Germany).

One senior US official says the interim deal agreed last November “over-performed in many respects,” because Iran “kept its commitments” to remove the stockpile of its most sensitive nuclear material – uranium enriched to 20 percent purity. Iran suspended other aspects of its program, too, and has permitted more access for UN inspectors, in exchange for modest sanctions relief worth less than $6 billion, as talks continued toward a final deal.

During six rounds of intensive talks in Vienna this year – including a 17-day marathon that ended on Friday – both sides showed flexibility on key issues, including changing the structure of the Arak heavy water reactor now under construction so that it produces less plutonium, another path to a bomb. Another discussion turned on changing the status of the deeply buried Fordow enrichment site to that of a research facility.

All told, the progress was enough for all sides to agree that four more months – to the Nov. 24 anniversary of the signing of the Geneva interim agreement – could be enough to seal a final deal. In the meantime, Iran will continue to receive further sanctions relief worth $2.8 billion, in exchange for further Iranian steps, like turning one-quarter of the oxide created by converting the 20-percent enriched stockpile into fuel plates, so there is even less chance it can be used for a bomb.

Those steps will enable the final diplomatic push needed in the months ahead. This may be the “last and best chance for a long time to end the nuclear argument peacefully,” says German Foreign Minister Frank-Walter Steinmeier.

Suspicions abound

Many Iranians suspect that the aim of the P5+1 – especially the US – goes beyond technically preventing Iran from ever getting a nuclear weapon. In this view, outside powers seek to deprive Iran of its “right” to nuclear power, and to constrict the Islamic Republic’s regional and global influence.

In the same vein, negotiators on the other side of the table may reckon that Iran wants only to get debilitating sanctions lifted and showcase its defiance, while maintaining a nuclear “threshold” status that can be quickly activated.

The goal of these talks, one senior US official said early Saturday, was to prevent Iran from obtaining a nuclear weapon, “which would allow them to project more power into the neighborhood…and obviously would be a threat to their neighbors and would probably set off a race for nuclear weapons."

Iran’s Supreme Leader Ayatollah Ali Khamanei, in remarks published last Monday, said Iran “should plan for the future, supposing the enemy won’t ease sanctions.” He said the P5+1 wanted to limit Iran, to accept 10,000 centrifuges “of the older type we already have.”

“Perhaps this is not a need this year or in two years or five years, but this is the country’s absolute need,” Khamenei said. He backed the negotiating team, but also praised domestic hardliners who have attacked the talks, saying, “moderation does not mean to prevent a believer from his duty.”

Interpretations

It was the first time Iran’s highest authority has spoken in such detail of figures on the table in the nuclear talks, or Iran’s needs, so his words sparked multiple interpretations, from seeing them as a move to pre-empt criticism of any compromise deal, to a new red line guaranteed to make the talks fail.

“It’s a strange and clever way to get the hardliners to accept limits,” says one analyst in Tehran who asked not to be named. The fact that Khamenei spoke about a future goal of industrial-scale enrichment could prevent attacks by hardliners against Iran’s negotiators today, he says, if they accept a temporary deal with far less capacity.

Yet critics themselves stepped in quickly: The hardline Kayhan newspaper stated that Khamenei’s figure of 190,000 was Iran’s new “definitive” red line that was now “obviously unchangeable.”